Microelectromechanical device having a common ground plane layer and a set of contact teeth and method for making the same

ABSTRACT

The present invention relates to MEM switches. More specifically, the present invention relates to a system and method for making MEM switches having a common ground plane. One method for making MEM switches includes: patterning a common ground plane layer on a substrate; forming a dielectric layer on the common ground plane layer; depositing a DC electrode region through the dielectric layer to contact the common ground plane layer; and depositing a conducting layer on the DC electrode region so that regions of the conducting layer contact the DC electrode region, so that the common ground plane layer provides a common ground for the regions of the conducting layer

RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. ProvisionalPatent Application No. 10/783,772, filed Feb. 20, 2004, entitledFABRICATION METHOD FOR MAKING A PLANAR CANTILEVER, LOW SURFACE LEAKAGE,REPRODUCIBLE AND RELIABLE METAL DIMPLE CONTACT MICRO-RELAY MEMS SWITCH.”

BACKGROUND OF THE INVENTION

(1) Technical Field

The present invention relates to a fabrication technique for amicro-electro-mechanical system (MEMS) micro relay switch to increasethe reliability, yield, and performance of its contacts. Specifically,the invention relates to a technique for producing amicroelectromechanical device having a common ground plane layer and aset of contact teeth.

(2) Discussion

Today, there are two types of MEMS switches for RF and microwaveapplications. One type is the capacitance membrane switch known as theshunt switch, and the other is the metal contact switch known as theseries switch. Besides the two types of switches mentioned above,designs can vary depending on the methods with which the switches areactuated. Generally, switch designs are based on either electrostatic,thermal, piezoelectric, or magnetic actuation methods.

The metal contact series switch is a true mechanical switch in the sensethat it toggles up (open) and down (close). One difference among themetal contact switch designs is in their armature structure. Forexample, switches from Sandia National Labs and Teravita Technologiesuse an all metal armature. MEMS switches from Rockwell use an armaturecomposed of a metal layer on top of an insulator and switches from HRLLaboratories, LLC use an insulating armature having a metal electrodethat is sandwiched between two insulating layers. Because of thedifference in armature designs, metal contacts in these devices are allfabricated differently; however, in each of these designs the metalcontacts are all integrated with part of the armature. The performanceof these switches is mainly determined by the metal contact and thearmature design. One important issue, occurring when the metal contactis part of the armature, relates to the fabrication process, whereinperformance may be sacrificed if the contact is not well controlled.

U.S. Pat. No. 6,046,659 issued Apr. 4, 2000to Loo et al. (herein afterreferred to as the “Loo Patent”) discloses two types ofmicro-electro-mechanical system (MEMS) switches, an I-switch and aT-switch. In the “Loo Patent,” both the I and T-MEMS switches utilize anarmature design, where one end of an armature is affixed to an anchorelectrode and the other end of the armature rests above a contactelectrode.

FIG. 1A depicts a top view of a T-switch 100 as disclosed in the priorart. A cross-section of the switch shown in FIG. 1A is shown in FIGS. 1Band 1C. In FIG. 1B the switch is in an open position, while in FIG. 1C,the switch is in a closed position. In this aspect, a radio-frequency(RF) input transmission line 118 and a RF-output transmission line 120are disposed on the substrate 114, shown in FIG. 1B. A conductingtransmission line 128 is disposed across one end of an armature 116,allowing for connection between the RF-input transmission line 118 andthe RF-output transmission line 120 when the switch is in the closedposition. One skilled in the art will appreciate that the cross-sectiononly shows the contact of the armature 116 with the RF-outputtransmission line 120, since the contact of the armature 116 with theRF-input transmission line 118 is directly behind the RF-outputtransmission line 120 when looking at the cross-section of the switch.Thus, for ease of explanation, FIGS. 1B and 1C will be discussedemphasizing the RF-output transmission line 120; however, the sameexplanation also holds for contacting of the RF-input transmission line118. Further, one skilled in the art will appreciate that the RF-inputand RF-output transmission lines are labeled as such for conveniencepurposes only and are interchangeable.

When the switch is in an open position, the transmission line 128 sitsabove (a small distance from) the RF-input transmission line 118 and theRF-output transmission line 120. Thus, the transmission line 128 iselectrically isolated from both the RF-input transmission line 118 andthe RF-output transmission line 120. Furthermore, because the RF-inputtransmission line 118 is not connected with the RF-output transmissionline 120, the RF signals are blocked and they cannot conduct from theRF-input transmission line 118 to the RF-output transmission line 120.

When the switch is in closed position, the conducting transmission line128 is in electrical contact with both the RF-output transmission line120, and the RF-input transmission line 118. Consequently, the threetransmission lines 120, 128, and 118 are connected in series to form asingle transmission line in order to conduct RF signals. The “LooPatent” also provides switches that have conducting dimples 124 and 124′attached with the transmission line 128 which define metal adhesionareas to improve contact characteristics.

FIG. 1B is a side view of a prior art micro-electro-mechanical system(MEMS) switch 100 of FIG. 1A in an open position. A conducting dimple124 protrudes from the armature 116 toward the RF-output transmissionline 120. The transmission line 128 (shown in FIG. 1A) is deposited onthe armature 116 and electrically connects the dimple 124 associatedwith the RF-output transmission line 120 to another dimple 124′associated with the RF-input transmission line 118.

FIG. 1C depicts the MEMS switch 100 of FIG. 1A in a closed state. When avoltage is applied between a cantilever bias electrode 130 and asubstrate bias electrode 122, an electrostatic attractive force willpull the cantilever bias electrode 130 as well as the attached armature116 toward the substrate bias electrode 122, and the (metal) contactdimple 124 will touch the RF-output transmission line 120. The contactdimple 124 associated with the RF-input transmission line 118 will alsocome into contact with the RF-input transmission line 118, thus throughthe transmission line 128 (shown in FIG. 1A) the RF-input transmissionline 118 is electrically connected with the RF-output transmission line120 when the switch is in a closed position. Note that in the FIG. 1A,the armature 116 is anchored to the substrate 114 by an anchor 132 andthat bias input signal pads 134 and 136 are provided for supplyingvoltage necessary for closing the switch 100.

FIG. 2A depicts a top view of an I-switch 200 as disclosed in the priorart. FIG. 2B depicts a direct current (DC) cross-section of the switch200 while, FIG. 2C depicts a RF cross-section of the switch 200. In FIG.2B, a DC signal is passed from the DC contact 220 through an anchorpoint 222 and into a DC cantilever structure 224. A substrate biaselectrode 226 is positioned on the substrate 114. As a DC bias isapplied to the DC contact 220 and the substrate bias electrode 226, theDC cantilever structure 224 is pulled toward the substrate 114, causingthe RF cantilever structure 215 (shown in FIG. 2C), shown in FIG. 2A, toalso be deflected toward the substrate 114. FIGS. 2D and 2E depict theswitch 200 in the closed position from the same perspectives as shown inFIGS. 2B and 2C, respectively.

FIG. 2C depicts the RF cross-section of switch 200. The RF-inputtransmission line 210 passes through anchor point 214 and into the RFcantilever structure 215. The metal dimple 216 protrudes from the RFcantilever structure 215. For ease of explanation the RF cantileverstructure 215 and the DC cantilever structure 224 are described hereinas two separate structures; however, one skilled in the art willappreciate that these two structures are typically made of one piece ofmaterial. The metal dimple 216 provides an electrical contact betweenthe RF-input transmission line 210 and the RF-output transmission line212. As discussed above, when a DC bias is applied to the DC contact 210and the substrate bias electrode 226 (shown in FIG. 2B), the RFcantilever structure 215 is deflected toward the substrate 114. Thedeflection of the RF cantilever structure 215 toward the substrate 114provides an electrical path between the RF-input transmission line 210and the RF-output transmission line 212. FIGS. 2D and 2E depict theswitch 200 in the closed position from the same perspectives as shown inFIGS. 2B and 2C, respectively. Note that in FIG. 2A the path shown inFIGS. 2B and 2D is depicted between 200 b and 200 b′ in and that thepath shown in FIGS. 2C and 2E is depicted between 200 c and 200 c′.

Both of the above-described switch types suffer from a bias-padcontact-related drawback in that when used for extensive periods, theregion of the switch near the bias pad tends to “stick” in a closedposition, effectively destroying the switch. Additionally, in arrays ofswitches, DC bias signals passed through a switch can cross-coupleneighboring switches, thereby causing the actuation of the neighboringswitches. The present invention overcomes these drawbacks by providing aset of “teeth” in the bias pad area to minimize adhesion and byproviding a common ground plane to isolate individual switches in anarray of switches, respectively.

SUMMARY

The present invention provides a system and a method that overcomes theaforementioned limitations and fills the aforementioned needs byproviding a common ground plane for MEMS switches.

One aspect of the invention is a method for forming a common ground foran electromechanical device comprising acts of: patterning a commonground plane layer on a substrate; forming a dielectric layer on thecommon ground plane layer; depositing a DC electrode region through thedielectric layer to contact the common ground plane layer; anddepositing a conducting layer on the DC electrode region so that regionsof the conducting layer contact the DC electrode region, so that thecommon ground plane layer provides a common ground for the regions ofthe conducting layer.

Another aspect of the invention is a method for forming a common groundfor an electromechanical device, wherein the act of patterning a commonground plane layer on a substrate further comprises acts of: depositinga ground plane photoresist pattern to form a common ground plane layeron at least a portion of a substrate having a substrate area; depositingthe common ground plane layer into the ground plane photoresist pattern;and removing the ground plane photoresist pattern.

Yet another aspect of the invention is a method for forming a commonground for an electromechanical device, wherein the act of forming adielectric layer on the common ground plane layer further comprises actsof: depositing a dielectric layer having a thickness and an area on thecommon ground plane layer; depositing a DC via photoresist pattern onthe dielectric layer, patterned to leave a DC electrode via exposed;etching through the thickness of a portion of the area of the dielectriclayer at the DC electrode via to form a DC via in the dielectric layer,where the DC via connects with the common ground plane layer; andremoving the DC via photoresist pattern.

Yet another aspect of the present invention is a method for forming acommon ground for an electromechanical device, wherein the act ofdepositing a conducting layer on the DC electrode region so that regionsof the conducting layer contact the DC electrode region, so that thecommon ground plane layer provides a common ground for the regions ofthe conducting layer further comprises acts of: depositing a DCelectrode region photoresist pattern; depositing a conducting layer onthe DC electrode region photoresist pattern and dielectric layer to forma set of DC electrodes in the set of DC electrode regions, where a DCelectrode is in contact with the common ground plane layer through theDC via; and removing the DC electrode region photoresist pattern.

Another aspect of the present invention is a method for forming a commonground for an electromechanical device, further comprising acts of:depositing a sacrificial layer over the conducting layer; depositing ananchor site photoresist pattern to provide for an anchor site; etchingthrough the sacrificial layer to expose a portion of the conductinglayer at a DC electrode region to form an anchor site; removing theanchor site photoresist pattern; depositing an insulating firststructure layer on the sacrificial layer and the anchor site, theinsulating first structure layer having an area; depositing a topelectrode photoresist pattern for etching through the anchor site forproviding contact to the conducting layer and for forming a topelectrode; etching through the insulating first structure layer acrossat least a portion of the anchor site so that a portion of theconducting layer is exposed, and etching through the insulating firststructure layer and through a portion of the thickness of thesacrificial layer at a top electrode site so that a top electrode spaceis defined through the insulating first structure layer, and into thesacrificial layer, proximate an electrode region; removing the topelectrode photoresist pattern; depositing a device separationphotoresist pattern on the insulating first structure layer, the deviceseparation photoresist pattern forming separation regions forelectrically separating desired areas of the electromechanical deviceand for separating desired devices; depositing a conducting secondstructure layer on the insulating first structure layer, the exposedportion of the conducting layer, and in the top electrode space, theconducting second structure layer having an area; removing the deviceseparation photoresist pattern to eliminate unwanted portions of theconducting second structure layer in order to electrically separatedesired areas of the electromechanical device and for separating desireddevices; depositing an insulating third structure layer on theelectromechanical device, across the substrate area, the insulatingthird structure layer having an area; depositing a device shapephotoresist pattern on the electromechanical device, across thesubstrate area, with the device shape photoresist pattern definingdesired device shapes by selective exposure; selectively etching throughexposed portions of the insulating first structure layer and theinsulating third structure layer to isolate an electromechanical devicehaving a desired shape; and removing the device shape photoresistpattern.

Another aspect of the present invention is method for forming a commonground for an electromechanical, further comprising acts of: depositinga sacrificial layer on the dielectric layer and the conducting layer,the sacrificial layer having a thickness; and etching a plurality oftooth regions into the sacrificial layer proximate a portion of theconducting layer, such that the tooth regions, in a final device,provide a reduced adhesion area when the device closes.

Yet another aspect of the present invention is a method for forming acommon ground for an electromechanical device, further comprising actsof: depositing an anchor site photoresist pattern to provide for ananchor site; etching through the sacrificial layer to an electroderegion in order to expose a portion of the conducting layer at a DCelectrode region to form an anchor site; removing the anchor sitephotoresist pattern; depositing an insulating first structure layer onthe sacrificial layer and the anchor site, the insulating firststructure layer having an area; depositing a top electrode photoresistpattern for etching through the anchor site for providing contact to theconducting layer and for forming a top electrode space; etching throughthe insulating first structure layer across at least a portion of theanchor site so that a portion of the conducting layer is exposed, andetching through the insulating first structure layer and through aportion of the thickness of the sacrificial layer at a top electrodesite so that a top electrode space is defined through the insulatingfirst structure layer, and into the sacrificial layer, proximate anelectrode region; removing the top electrode photoresist pattern;depositing a device separation photoresist pattern on the insulatingfirst structure layer, the device separation photoresist pattern formingseparation regions for electrically separating desired areas of theelectromechanical device and for separating desired devices; depositinga conducting second structure layer on the insulating first structurelayer, the exposed portion of the conducting layer, and in the topelectrode space, the conducting second structure layer having an area;removing the device separation photoresist pattern to eliminate unwantedportions of the conducting second structure layer in order toelectrically separate desired areas of the electromechanical device andfor separating desired devices; depositing an insulating third structurelayer on the electromechanical device, across the substrate area, theinsulating third structure layer having an area; depositing a deviceshape photoresist pattern on the electromechanical device, across thesubstrate area, with the device shape photoresist pattern definingdesired device shapes by selective exposure; selectively etching throughexposed portions of the insulating first structure layer and theinsulating third structure layer to isolate an electromechanical devicehaving a desired shape; and removing the device shape photoresistpattern.

Another aspect of the invention is a method for forming a common groundfor an electromechanical device, wherein the act of forming a dielectriclayer on the common ground plane layer further comprises acts of:depositing a dielectric layer having a thickness and an area on thecommon ground plane layer; depositing a DC via photoresist pattern onthe dielectric layer, patterned to leave a DC electrode via exposed;etching through the thickness of a portion of the area of the dielectriclayer at the DC electrode via to form a DC via in the dielectric layer,where the DC via connects with the common ground plane layer; andremoving the DC via photoresist pattern.

Yet another aspect of the present invention is a method for forming acommon ground for an electromechanical device, wherein the act ofdepositing a conducting layer on the DC electrode region so that regionsof the conducting layer contact the DC electrode region, so that thecommon ground plane layer provides a common ground for the regions ofthe conducting layer further comprises acts of: forming a DC electrodein set of DC electrode regions, where a DC electrode is in contact withthe common ground plane layer through the DC via.

Another aspect of the present invention is a method for forming a commonground for an electromechanical device, further comprising acts of:depositing a sacrificial layer, the sacrificial layer having athickness; and etching a plurality of tooth regions into the sacrificiallayer proximate a portion of the conducting layer, such that the toothregions, in a final device, provide a reduced adhesion area when thedevice closes.

Yet another aspect of the present invention is a method for forming acommon ground for an electromechanical device, further comprising actsof: depositing an anchor site photoresist pattern to provide for ananchor site; etching through the sacrificial layer to an electroderegion in order to expose a portion of the conducting layer at a DCelectrode region to form an anchor site; removing the anchor sitephotoresist pattern; depositing an insulating first structure layer onthe sacrificial layer and the anchor site, the insulating firststructure layer having an area; depositing a top electrode photoresistpattern for etching through the anchor site for providing contact to theconducting layer and for forming a top electrode space; etching throughthe insulating first structure layer across at least a portion of theanchor site so that a portion of the conducting layer is exposed, andetching through the insulating first structure layer and through aportion of the thickness of the sacrificial layer at a top electrodesite so that a top electrode space is defined through the insulatingfirst structure layer, and into the sacrificial layer, proximate anelectrode region; removing the top electrode photoresist pattern;depositing a device separation photoresist pattern on the insulatingfirst structure layer, the device separation photoresist pattern formingseparation regions for electrically separating desired areas of theelectromechanical device and for separating desired devices; depositinga conducting second structure layer on the insulating first structurelayer, the exposed portion of the conducting layer, and in the topelectrode space, the conducting second structure layer having an area;removing the device separation photoresist pattern to eliminate unwantedportions of the conducting second structure layer in order toelectrically separate desired areas of the electromechanical device andfor separating desired devices; depositing an insulating third structurelayer on the electromechanical device, across the substrate area, theinsulating third structure layer having an area; depositing a deviceshape photoresist pattern on the electromechanical device, across thesubstrate area, with the device shape photoresist pattern definingdesired device shapes by selective exposure; selectively etching throughexposed portions of the insulating first structure layer and theinsulating third structure layer to isolate an electromechanical devicehaving a desired shape; and removing the device shape photoresistpattern.

Yet another aspect of the invention is a method of forming tooth regionson a metal portion of an electromechanical device comprising acts of:etching a plurality of tooth regions in to a sacrificial layer proximatea portion of a conducting layer; and depositing a metal layer over thesacrificial layer such that portions of the metal layer conform with thetooth regions to form teeth; whereby the conducting layer may be urgedinto contact with another portion of the electromechanical device withthe teeth providing a reduced adhesion area.

Another aspect of the present invention is a method of forming toothregions on a metal portion of an electromechanical device, furthercomprising acts of: patterning a conducting layer on a substrate suchthat portions of the conducting layer form electrodes; and depositing asacrificial layer on portions of the substrate and the conducting layer,where the sacrificial layer deposited is the sacrificial layer intowhich tooth regions are etched.

Yet another aspect of the present invention is a method of forming toothregions on a metal portion of an electromechanical device, furthercomprising acts of: depositing an anchor site photoresist pattern toprovide for an anchor site; etching through the sacrificial layer to anelectrode region in order to expose a portion of the conducting layer ata DC electrode region to form an anchor site; removing the anchor sitephotoresist pattern; depositing an insulating first structure layer onthe sacrificial layer and the anchor site, the insulating firststructure layer having an area; depositing a top electrode photoresistpattern for etching through the anchor site for providing contact to theconducting layer and for forming a top electrode space; etching throughthe insulating first structure layer across at least a portion of theanchor site so that a portion of the conducting layer is exposed, andetching through the insulating first structure layer and through aportion of the thickness of the sacrificial layer at a top electrodesite so that a top electrode space is defined through the insulatingfirst structure layer, and into the sacrificial layer, proximate anelectrode region; removing the top electrode photoresist pattern;depositing a device separation photoresist pattern on the insulatingfirst structure layer, the device separation photoresist pattern formingseparation regions for electrically separating desired areas of theelectromechanical device and for separating desired devices; depositinga conducting second structure layer on the insulating first structurelayer, the exposed portion of the conducting layer, and in the topelectrode space, the conducting second structure layer having an area;removing the device separation photoresist pattern to eliminate unwantedportions of the conducting second structure layer in order toelectrically separate desired areas of the electromechanical device andfor separating desired devices; depositing an insulating third structurelayer on the electromechanical device, across the substrate area, theinsulating third structure layer having an area; depositing a deviceshape photoresist pattern on the electromechanical device, across thesubstrate area, with the device shape photoresist pattern definingdesired device shapes by selective exposure; selectively etching throughexposed portions of the insulating first structure layer and theinsulating third structure layer to isolate an electromechanical devicehaving a desired shape; and removing the device shape photoresistpattern.

Yet another aspect of the invention is a common ground for anelectromechanical device comprising: a substrate layer; a common groundplane layer formed on a portion of the substrate layer; a dielectriclayer formed on the common ground plane layer and the substrate layer,the dielectric layer formed with conductor spaces therein, where atleast one of the conductor spaces is in contact with the ground metallayer, the dielectric layer further including a dielectric top surface;and a conducting layer formed as a set of conductors in the conductorspaces of the dielectric layer, with at least one of the conductors incontact with the common ground plane layer, the conducting layer havinga conducting layer top surface, and where the dielectric top surface andthe conducting layer top surface are formed in a substantially co-planarfashion to provide a planarized substrate structure.

Another aspect of the invention is a set of tooth regions formed on ametal portion of an electromechanical device comprising: a plurality oftooth regions formed from a portion of a conducting layer, whereby theconducting layer may be urged into contact with another portion of theelectromechanical device with the tooth regions providing a reducedadhesion area.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will beapparent from the following detailed descriptions of the preferredaspect of the invention in conjunction with reference to the followingdrawings, where:

FIG. 1A is a top view of a prior art T-MEMS switch;

FIG. 1B is a side-view of the prior art T-MEMS switch presented in FIG.1A, in an open position;

FIG. 1C is a side-view of the prior art T-MEMS switch presented in FIG.1A, in a closed position;

FIG. 2A is a top view of a prior art I-MEMS switch;

FIG. 2B is a side-view of the DC cross-section of the prior art I-MEMSswitch presented in FIG. 2A, in an open position;

FIG. 2C is a side-view of the RF cross-section of the prior art I-MEMSswitch presented in FIG. 2A, in an open position;

FIG. 2D is a side-view of the DC cross-section of the prior art I-MEMSswitch presented in FIG. 2A, in a closed position;

FIG. 2E is a side-view of the RF cross-section of the prior art I-MEMSswitch presented in FIG. 2A, in a closed position;

FIG. 3A is a top view of a T-MEMS switch in accordance with the presentinvention;

FIG. 3B is a side-view of the T-MEMS switch presented in FIG. 3A, in anopen position;

FIG. 3C is a cross-section of the T-MEMS presented in FIG. 3A, in theopen position, where the cross section is taken along a line throughelectrodes 340 and 338;

FIG. 3D is a side-view of the T-MEMS presented in FIG. 3A, in a closedposition;

FIG. 3E is a cross-section of the T-MEMS switch presented in FIG. 3A, inthe closed position, where the cross section is taken along a linethrough electrodes 340 and 338;

FIG. 4A is a side view of a DC cross-section of an I-MEMS switch in anopen position in accordance with the present invention;

FIG. 4B is a side view of a RF cross-section of the I-MEMS switchpresented in FIG. 4A, in an open position;

FIG. 4C is a side view of the DC cross-section of the I-MEMS switchpresented in FIG. 4A, in a closed position;

FIG. 4D is a side view of the RF cross-section of the I-MEMS switchpresented in FIG. 4A, in a closed position;

FIG. 5A depicts a side view of a cross-section of a doubly supportedcantilever beam MEMS switch in an open position in accordance with thepresent invention;

FIG. 5B depicts a side view of a cross-section of a doubly supportedcantilever beam MEMS switch presented in FIG. 5A, in a closed position;

FIGS. 6A through 6P are side-views of a T-MEMS switch of the presentinvention, showing the switch at various stages of production;

FIG. 7 is a table presenting various non-limiting examples of materials,deposition processes (where applicable), removal processes (whereapplicable), etch processes (where applicable), and thickness ranges forthe various layers that make up a MEMS switch according to the presentinvention;

FIG. 8 is an illustrative diagram of a computer program product aspectof the present invention; and

FIG. 9 is a block diagram of a data processing system used inconjunction with the present invention.

DETAILED DESCRIPTION

The present invention relates to fabrication techniques for increasingthe reliability and performance of contacts in micro-electro-mechanicalsystem (MEMS) switches. Specifically, the invention relates to thefabrication of a planar cantilever beam, lower surface leakage, a morereliable metal contact dimple design and a high yield process. Thefollowing description, taken in conjunction with the referenceddrawings, is presented to enable one of ordinary skill in the art tomake and use the invention and to incorporate it in the context ofparticular applications. Various modifications, as well as a variety ofuses in different applications, will be readily apparent to thoseskilled in the art, and the general principles defined herein, may beapplied to a wide range of aspects. Thus, the present invention is notintended to be limited to the aspects presented, but is to be accordedthe widest scope consistent with the principles and novel featuresdisclosed herein. Furthermore, it should be noted that unless explicitlystated otherwise, the figures included herein are illustrateddiagrammatically and without any specific scale, as they are provided asqualitative illustrations of the concept of the present invention.

In the following detailed description, numerous specific details are setforth in order to provide a more thorough understanding of the presentinvention. However, it will be apparent to one skilled in the art thatthe present invention may be practiced without necessarily being limitedto these specific details. In other instances, well-known structures anddevices are shown in block diagram form, rather than in detail, in orderto avoid obscuring the present invention.

The reader's attention is directed to all papers and documents which arefiled concurrently with this specification and which are open to publicinspection with this specification, and the contents of all such papersand documents are incorporated herein by reference. All the featuresdisclosed in this specification, (including any accompanying claims,abstract, and drawings) may be replaced by alternative features servingthe same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

Furthermore, any element in a claim that does not explicitly state“means for” performing a specified function, or “step for” performing aspecific function, is not to be interpreted as a “means” or “step”clause as specified in 35 U.S.C. Section 112, Paragraph 6. Inparticular, the use of “step of ” or “act of” in the claims herein isnot intended to invoke the provisions of 35 U.S.C. 112, Paragraph 6.

In order to provide a working frame of reference, first a glossary ofterms used in the description and claims is provided. Next, a discussionof various principal aspects of the present invention is provided.Third, an introduction is presented to provide the reader with a generalunderstanding of the present invention. Fourth, a discussion is providedto give an understanding of the specific details of the presentinvention. Fifth, experimental results are provided for the reader tohave a better understanding of the invention in actual use. Finally, aconclusion is provided to summarize key aspects of the presentinvention.

(1) Glossary

Before describing the specific details of the present invention, acentralized location is provided in which various terms used herein andin the claims are defined. The glossary provided is intended to providethe reader with a general understanding for the intended meaning of theterms, but is not intended to convey the entire scope of each term.Rather, the glossary is intended to supplement the rest of thespecification in more accurately explaining the terms used.

Actuation portion: A part of a switch that moves to connect ordisconnect an electrical path. Some examples include an armature and acantilever.

Cantilever: A beam that sits above the substrate. It is affixed at themetal contact electrode at one end, and suspended freely above the RFelectrodes at the opposite end.

Common ground: A conductive layer positioned proximate a group ofcontacts to provide a common ground reference to eliminate stray(undesired) signals from affecting neighboring (other) devices.

Metal dimple portion: An area of metal that protrudes from an armatureproviding increased contact reliability in MEMS switches. Also referredto as a metal dimple contact.

Tooth: A surface feature created proximate a adhesion area of the switchthat minimizes the adhesion in order to ensure proper release of theswitch after closure.

(2) Principal Aspects

The present invention has three principal aspects. The first is a MEMSswitch with a set of teeth formed proximate an armature bias pad tominimize surface area adhesion and a common ground layer to provide acommon (reference) ground for a plurality of devices. The MEMS switchincludes an actuating portion which moves from a first position to asecond position, where in the second position the switch provides a pathfor an RF signal. A metal dimple is desirably placed on a portion of thecantilever beam that contacts metal on the RF electrodes on thesubstrate when the MEMS switch is closed. The present invention alsoteaches a fabrication method (and products by the method) that providesa set of contact teeth along with a common ground layer in order tomanufacture MEMS switches having high yield and improved performancereliability. Additionally, the various acts in a method according to thepresent invention may be automated and computer-controlled, the presentinvention also teaches a computer program product in the form of acomputer readable media containing computer-readable instructions foroperating machinery to perform the various acts required to make a MEMSswitch according to the present invention. These instructions may bestored on any desired computer readable media, non-limiting examples ofwhich include optical media such as compact discs (CDs) and digitalversatile discs (DVDs), magnetic media such as floppy disks and harddrives, and circuit-based media such as flash memories andfield-programmable gate arrays (FPGAs). The computer program productaspect will be discussed toward the end of this description.

FIG. 3A is a top view of a T-MEMS switch 300. An armature 336 allows foran electrical connection between a first RF transmission line, i.e. anRF-input transmission line 340 and a second RF transmission line, i.e.an RF-output transmission line 338, when the switch is in a closedposition.

FIG. 3B shows one side-view cross-section of the T-MEMS switch 300. Oneskilled in the art will appreciate that the cross-section only shows thecontact of the armature 336 with the RF-output transmission line 338,since the contact of the RF-input transmission line 340 (shown in FIG.3A) is directly behind the RF-output transmission line 338 when lookingat the cross-section of the switch. One end of the armature 336 isaffixed to an anchor electrode 332 on a substrate 114. The other end ofthe armature 336 is positioned over the RF-line which is divided intotwo separate sections, the RF-input transmission line 340 and theRF-output transmission line 338. The RF-input transmission line 340 andthe RF-output transmission line 338 are separated by a gap (visible inFIG. 3A). A substrate bias electrode 342 is attached with the substrate114 below the armature 336. The armature 336 sits above the substratebias electrode 342 and is electrically isolated from the substrate biaselectrode 342 by an air gap forming a parallel plate capacitor when theMEMS switch 300 is in an “open” position. An output top dimple electrode345 a is placed on one end of the armature 336 above the output RFtransmission line 338. Similarly, an input top dimple electrode 345 b(visible in FIG. 3A) is placed on the end of the armature 336 above theinput RF transmission line 340, shown in FIG. 3C. The output top dimpleelectrode 345 a and the input top dimple electrode 345 b areelectrically connected via a transmission line 348, shown in FIG. 3A. Inone aspect, the transmission line 348 is a metal film transmission lineembedded inside the armature 336.

In order to minimize the adhesion between the portion of the armatureproximate a cantilever bias electrode 350 and the substrate biaselectrode 342 when the switch 300 is closed, a set of teeth 370 isprovided, formed in the first structure layer of the armature.Furthermore, a common ground layer 372 formed under a dielectric layer374 provides a common ground contact through vias 376 to the anchorelectrode 332 through a dielectric layer 374.

FIG. 3D depicts the cross-section of the T-MEMS switch 300 in FIG. 3B ina closed state. When a voltage is applied between the cantilever biaselectrode 350 and the substrate bias electrode 342, an electrostaticattractive force will pull the cantilever bias electrode 350 as well asthe attached armature 336 towards the substrate bias electrode 342.Consequently, the output top dimple electrode 345 a touches the outputRF transmission line 338 and the input top electrode 345 b (visible inFIG. 3A) touches the input RF transmission line 340 (shown in FIG. 3E)providing a good electrical contact. Thus, the output top dimpleelectrode 345 a, the transmission line 348 (visible in FIG. 3A), theinput top dimple electrode 345 b (visible in FIG. 3A) provide anelectrical path for bridging the gap between the RF-input transmissionline 340 and the RF-output transmission line 338, thereby closing theMEMS switch 300.

The substrate 114 may be comprised of a variety of materials. If theMEMS switch 300 is intended to be integrated with other semiconductordevices (i.e., with low-noise high electron mobility transistor (HEMT)monolithic microwave integrated circuit (MMIC) components), it isdesirable to use a semi-insulating semiconducting substance such asgallium arsenide (GaAs), indium phosphide (InP) or silicon germanium(SiGe) for the substrate 114. This allows the circuit elements as wellas the MEMS switch 300 to be fabricated on the same substrate usingstandard integrated circuit fabrication technology such as metal anddielectric deposition, and etching by using the photolithographicmasking process. Other possible substrate materials include silicon,various ceramics, and quartz. The flexibility in the fabrication of theMEMS switch 300 allows the switch 300 to be used in a variety ofcircuits. This reduces the cost and complexity of circuits designedusing the present MEMS switch.

In the T-MEMS switch (see FIGS. 3A-3E), when actuated by electrostaticattraction, the armature 336 bends towards the substrate 114. Thisresults in the output top dimple electrode 345 a and the input topdimple electrode 345 b on the armature 336 contacting the output RFtransmission line 338 and input RF transmission line 340 respectively,and the armature 336 bending to allow the cantilever bias electrode 350to physically contact the substrate bias electrode 342. This fullyclosed state is shown in FIG. 3E. The force of the metallic contactbetween the output RF transmission line 338 and the output top dimpleelectrode 345 a (also the input RF transmission line 340 and the inputtop dimple electrode 345 b) is thus dependent on the spring constantforce at the RF-output transmission line 340 and RF-input transmissionline 338 when the switch is closed. Metallic switches that do not haveprotruded dimple contact designs have contacts that depend upon thewhole armature flexibility and bias strength. It is considered that thistype of metal contact T-switch is less reliable than the micro-relayswitches with protruded dimple contacts such as those taught here. Inaddition to improving the switch reliability, the quality of the contactitself is improved by the dimple because the dimple has controllablegeometric features such as size (area and height) and shape. Thus, MEMSswitches without the dimples 345 a and 345 b are more likely to havetime-varying contact characteristics, a feature that may make themdifficult or impossible to use in some circuit implementations.

One skilled in the art will appreciate that the RF-input transmissionline 340 may be permanently attached with one end of the transmissionline 348 in the armature 336. In this case, the switch 300 is open whena gap exists between the RF-output transmission line 338 and thetransmission line 348. Further, one skilled in the art will appreciatethat the RF-output transmission line 338 may be permanently attachedwith one end of the transmission line 348 in the armature 336. In thiscase the switch is open when a gap exists between the RF-inputtransmission line 340 and the transmission line 348.

Finally, although the top dimple electrodes 345 a and 345 b are shown ina desirable manner that provides a locking mechanism, sandwiching alayer of the armature therein, it should be appreciated by one of skillin the art that the particular top dimple electrode configuration usedis not critical, and therefore any known or future configuration may beused.

FIG. 4A depicts a DC cross-section of an I-MEMS switch 400 in accordancewith the present invention. Depicted in FIG. 4A, a DC signal is passedfrom the DC contact 420 through an anchor point 422 and into the DCcantilever structure 424. In the cross-sectional view of FIG. 4A, aportion of a metal dimple 416 (shown in FIG. 4B) would be seen in thebackground if the RF portion of the switch 400 were shown. A substratebias electrode 426 is positioned on the substrate 114. As a DC bias isapplied to the DC contact 420 and the substrate bias electrode 426, theDC cantilever structure 424 is pulled toward the substrate 114. FIGS. 4Cand 4D depict the switch of FIGS. 4A and 4B, respectively, in a closedposition.

In order to minimize the contact between the portion of the armatureproximate a cantilever bias electrode 450 and the substrate biaselectrode 426 when the switch 400 is closed, a set of teeth 470 isprovided, formed in the first structure layer of the armature.Furthermore, a common ground layer 472 formed under a dielectric layer474 provides a common ground contact through vias 476 to the anchorelectrode 452 through a dielectric layer 474.

FIG. 4B depicts the RF cross-section of switch 400. The RF-inputtransmission line 410 passes through anchor point 414 and into the RFcantilever structure 415. Upon contact, the metal dimple 416 allowselectricity to passes through the RF cantilever structure 415. The metaldimple 416 also provides an electrical contact between the RF-inputtransmission line 410 and the RF-output transmission line 412 when theswitch is in a closed position. As discussed above, when a DC bias isapplied to the DC contact 420 and the substrate bias electrode 426, theDC cantilever structure 424 is pulled toward the substrate 114. Thedeflection of the DC cantilever structure 424 toward the substrate 114also causes the RF cantilever structure 415 to bend toward the substrate114, providing an electrical path between the RF-input transmission line410 and the RF-output transmission line 412.

In the I-MEMS switch (see FIGS. 4A-4D), the gap between the RF-outputtransmission line 412 and the metal dimple 416 is smaller than the gapbetween the substrate bias electrode 426 and the cantilever biaselectrode in the armature 424. When actuated by electrostaticattraction, the armature structure, comprising the DC cantileverstructure 424 and the RF cantilever structure 415, bends towards thesubstrate 114. First, the metal dimple 416 on the RF cantileverstructure 415 contacts the RF transmission line 416, at which point thearmature bends to allow the DC cantilever structure 424 to physicallycontact the substrate bias electrode 426. This fully closed state isshown in FIGS. 4C and 4D. The force of the metallic contact between theRF transmission line 412 and the metal dimple 416 is thus dependent onthe spring constant force at the RF transmission line 412 when theswitch is closed. Existing metallic switches that do not have contactdimples have contacts that depend upon the whole armature flexibilityand bias strength. It is considered that this type of metal contactT-switch is less reliable than the micro-relay switches with dimplecontacts such as those taught by the present invention. In addition toimproving the switch reliability, the quality of the contact itself isimproved by the dimple because the dimple has controllable geometricfeatures such as size (area and height) and shape. Thus, MEMS switcheswithout the dimple contact are more likely to have time-varying contactcharacteristics, a feature that may make them difficult or impossible touse in some circuit implementations.

Finally, although the top dimple electrode 416 is shown in a desirablemanner that provides a locking mechanism, sandwiching a layer of thearmature therein, it should be appreciated by one of skill in the artthat the particular top dimple electrode configuration used is notcritical, and therefore any known or future configuration may be used.

FIG. 5A depicts a cross-section of a doubly supported cantilever beamMEMS switch 500. An RF-input transmission line 510 is included in acantilever beam 512. An RF-output transmission line 514 is located on asubstrate 114. The cantilever beam 512, unlike the switches previouslydiscussed, is attached with the substrate 114 at two ends. Thecantilever beam 512 also includes a cantilever bias electrode 516. Asubstrate bias electrode 518 is located on the substrate 114. When a DCbias is applied to the cantilever bias electrode 516 and the substratebias electrode 518, the cantilever beam 512 moves from the openposition, shown in FIG. 5A to a closed position, shown in FIG. 5B. Inthe closed position, an electrical path is created between the RF-inputtransmission line 510 and the RF-output transmission line 514. Note thatrather than passing along the beam, the RF signal could also be passedfrom an RF-input transmission line to an RF-output transmission line byusing a line with a pair of dimples.

In order to minimize the contact between the portion of the armatureproximate the cantilever bias electrode 516 and the substrate biaselectrode 518 when the switch 500 is closed, a set of teeth 570 isprovided, formed in the first structure layer of the armature.Furthermore, a common ground layer 572 formed under a dielectric layer574 provides a common ground contact through vias 576 to the anchorelectrode 552 through a dielectric layer 574.

As discussed above, the prior art T-MEMS switches have dimples attachedwith the armature. Because the formation of the dimple in the armaturerequires a highly sensitive, time-controlled etching process, the yieldand performance of the MEMS switches will vary from lot to lot. However,with the design disclosed herein, by placing metal platforms on theinput and output RF electrodes that are protruded from the substrate(instead of having a deep dimple on the armature), the yield andperformance of MEMS switch fabrication is increased. A few of thepotential applications of these MEMS switches are in the RF, microwave,and millimeter wave circuits, and wireless communications spaces. Forexample, these MEMS switches can be used in commercial satellites,antenna phase shifters for beam-steering, and multi-band and diversityantennas for wireless cell phones and wireless local area networks(WLANS).

Finally, although the top dimple electrode 580 is shown in a desirablemanner that provides a locking mechanism, sandwiching a layer of thearmature therein, it should be appreciated by one of skill in the artthat the particular top dimple electrode configuration used is notcritical, and therefore any known or future configuration may be used.

The following is an exemplary set of operations that may be used in themanufacturing of the device disclosed herein. One skilled in the artwill appreciate that the acts outlined are to assist in incidatingchanges from the prior art manufacturing process, and are not intendedto be a complete list of all acts used in the process. One skilled inthe art will appreciate that the MEMS switches may have varying designs,such as I configurations and T configurations. However, themanufacturing acts disclosed herein are for the formation of afabrication method for making a reliable microrelay MEMS switch on asubstrate, which may be utilized in any MEMS switch configuration. Themanufacturing process is described using the terminology for the Iconfiguration as an illustration, however, those of skill in the artwill realize that the acts presented are readily adaptable for otherswitch types.

FIG. 6 depicts a substrate. As shown in FIG. 6A, a common ground planelayer 600 is deposited on a substrate 602. In particular, to completethe device to the point shown in FIG. 6A, first a ground planephotoresist pattern is deposited on the substrate. Second, the commonground plane layer 600, of a conductive material, is deposited over theground plane photoresist pattern and portions of the substrate 602.Next, the ground plane photoresist is removed, leaving the finishedground plane layer 600.

Next, as shown in FIG. 6B, a dielectric layer (typically Si₃N₄) 604having a thickness and an area is deposited on over the common groundplane layer 600 and a portion of the substrate 602. The deposition ofthe dielectric layer 604 is typically by by Plasma Enhanced ChemicalVapor Deposition (PECVD) or by Low Pressure Chemical Vapor Deposition(LPCVD).

As shown in FIG. 6C, next, a DC via 606 is formed through the dielectriclayer 604 to the common ground plane layer 600. To complete the deviceto the point shown in FIG. 6C, starting with the structure shown in FIG.6B, first a DC via photoresist pattern is deposited onto the dielectriclayer 604. Next, an etch process is used to form the DC via 606 throughthe dielectric layer 604 to the common ground plane layer 600. Finally,the DC via photoresist pattern is removed, leaving the DC via 606.

FIG. 6D presents the device shown in FIG. 6C, where the DC via 606 isfilled to form a filled DC via 608. As can be appreciated by one ofskill in the art, the DC via 606 may be filled either at this point, orlater during the formation of the DC electrodes with the same result.

FIG. 6E depicts the device of FIG. 6D with the addition of a substrateelectrode region photoresist pattern 610. To form the substrateelectrode photoresist pattern 610, first a photoresist layer is formedand then areas of the photoresist layer are removed (typically byetching) to create the pattern.

After the substrate electrode photoresist pattern 610 has beendeposited, next a conductive material (metal) layer is deposited intothe substrate electrode photoresist pattern 610, resulting in theplanarized configuration shown in FIG. 6F, having DC electrodes 614 and614 b, and RF electrode 614 c. Note that although three electrodes arepresented here, in the combination of two DC electrodes and one RFelectrode, the present invention is not limited to this configurationand that any combination of electrodes may be produced, as necessitatedby a particular application of the process.

At this point, the common ground has been formed. This technique can beextended to any device requiring such a common ground, and is notlimited to use with the acts described below.

After the common ground has been completed, a sacrificial layer 616 isdeposited on the device, as shown in FIG. 6G.

Next, a top electrode 618 is formed in the sacrificial layer 616, asshown in FIG. 6H. The formation of the top electrode 618 is accomplishedby first etching a top electrode site in the sacrificial layer 616, andfilling the top electrode site with conductive material to form the topelectrode 618.

After the top electrode has been completed, an anchor site 620 is formedin the sacrificial layer 616. To do so, first an anchor site photoresistpattern is formed on the sacrificial layer 616. Next, an etch is madethrough the anchor site photoresist pattern to an electrode region 614a. Then, the anchor site photoresist pattern is removed. This results inthe structure shown in FIG. 6I.

Next, as shown in FIG. 6J, a set of tooth regions 624 into thesacrificial layer 616 proximate a DC electrode 626. As will beappreciated by one of skill in the art, acts performed on a single layersuch as those depicted in FIG. 6H-J may be performed various ordersdepending on the particular needs of a specific process. To a similarextent, the order of the acts shown in all of FIG. 6 may be variedwithout departing from the scope of the present invention. Note alsothat the formation of the tooth regions 624 and subsequent actsregarding the teeth may be performed separately from other acts in thismethod, and thus are applicable to any device where minimal adhesion isdesired.

Next, to form the device shown in FIG. 6K, a first insulating structurelayer 628 is formed on the sacrificial layer 616. Also, althoughcritical only to the generation of the particular electrode-type shown,a top electrode via 630 is formed in the sacrificial layer 616.Typically, the area of the anchor site 620 and an area of the topelectrode 618 are masked with photoresist prior to the deposition of thefirst insulating structure layer 628, and then the photoresist isremoved, leaving the structure of FIG. 6K.

FIG. 6L shows the device of FIG. 6K with the addition of a conductivematerial into the top electrode via 630, forming a filled top electrodevia 632. The filling of the top electrode via 630 is typicallyaccomplished by masking the surrounding area with a photoresist layer,filling the top electrode via 630, and removing the photoresist layer,leaving the filled top electrode via 632.

After the top electrode via 630 has been filled, next, a deviceseparation photoresist pattern 634 is deposited over portions of theinsulating first structure layer 628 where metal deposition isundesirable. This provides for electrical separation of desired areas ofthe electromechanical device and for the separation of desired devices.Next, a conducting second structure layer 636 is deposited. Note that asshown, the conducting second structure layer 636 contacts with theelectrode region 614 a through the anchor site 620 and with the filledtop electrode via 632, resulting in the device shown in FIG. 6M.

Subsequently, the device separation photoresist pattern 634 is removedand a third insulating structure layer 638 having an area is depositedacross the substrate area. Although not shown, additional acts areperformed to complete the device separation. First, a device shapephotoresist pattern is deposited across the substrate area, with thedevice shape photoresist pattern defining desired device shapes byselective exposure. Next, a selective etch is performed through exposedportions of the insulating first structure layer and the insulatingthird structure layer to isolate an electromechanical device having adesired shape. Finally, the device shape photoresist pattern is removed,resulting in the device shown in FIG. 6N.

FIG. 6O shows the device of FIG. 6N in a “closed” position, where theteeth 640 minimize the contact in the area of the substrate electrode614 b.

FIG. 6P shows a top view of the switch of FIGS. 6O and 6N without thearmature. The common ground layer 600 can be seen extending under the DCelectrodes 614 a and 614 b as well as under the DC via 606. Also, it isnoteworthy that the RF electrodes 614 c are not within the perimeter ofthe common ground layer 600.

It is important to note that the set of tooth regions 624 may be formedeither on the armature region of a switch, as shown in FIG. 6 orprotruding from the substrate region or a bottom electrode. Further,depending on the layer structure of a particular device, the toothregions 624 may be formed as part of an insulating layer, a conductinglayer, or any combination of layers without departing from the scope ofthe present invention. Regardless of the geometric location, theconfiguration, or the material structure of the tooth regions 624, theirpurpose is for the reduction of the adhesion area at a place where oneportion of a device contacts another portion of a device (regardlesswhether the other portion is even of the same device).

In one aspect, the chip size containing the MEMS switch, such as thosetaught herein is 800×400 microns. The metal electrode pad is on theorder of 100×100 microns. The actuation pad may vary from 100−20×100−20microns depending upon the design of the specific actuation voltage. TheRF line may vary between 50-200 microns wide. The above dimensions areprovided as exemplary and are not intended to be construed as limiting.Instead, one skilled in the art will appreciate that differentdimensions may be used depending upon the size of the MEMS switch beingdesigned and the application for which it is being used. Furthermore, atable is presented in FIG. 7, providing non-limiting examples ofmaterials, deposition processes (where applicable), removal processes(where applicable), etch processes (where applicable), and thicknessranges for the various layers that make up a MEMS switch according tothe present invention. It is important that this table be consideredsimply as a general guide and that it be realized that the presentinvention may use other materials, deposit processes, removal processes,etch processes, and thicknesses than those described and that theinformation provided in FIG. 7 is intended simply to assist the readerin gaining a better general understanding of the present invention.

As stated previously, the operations performed by the present inventionmay be encoded as a computer program product. The computer programproduct generally represents computer readable code stored on a computerreadable medium such as an optical storage device, e.g., a compact disc(CD) or digital versatile disc (DVD), or a magnetic storage device suchas a floppy disk or magnetic tape. Other, non-limiting examples ofcomputer readable media include hard disks, read only memory (ROM), andflash-type memories. An illustrative diagram of a computer programproduct embodying the present invention is depicted in FIG. 8. Thecomputer program product is depicted as a magnetic disk 800 or anoptical disk 802 such as a CD or DVD. However, as mentioned previously,the computer program product generally represents computer readable codestored on any desirable computer readable medium.

When loaded onto a semiconductor process control computer as shown inFIG. 9, the computer instructions from the computer program productprovides the information necessary to cause the computer to perform theoperations/acts described with respect to the method above, resulting ina device according to the present invention.

A block diagram depicting the components of a computer system that maybe used in conjunction with the present invention is provided in FIG. 9.The data processing system 900 comprises an input 902 for receivinginformation from at least a computer program product or from a user.Note that the input 902 may include multiple “ports.” The output 904 isconnected with a processor 906 for providing information regardingoperations to be performed to various semiconductor processingmachines/devices. Output may also be provided to other devices or otherprograms, e.g. to other software modules for use therein or to displaydevices for display thereon. The input 902 and the output 904 are bothcoupled with the processor 906, which may be a general-purpose computerprocessor or a specialized processor designed specifically for use withthe present invention. The processor 906 is coupled with a memory 908 topermit storage of data and software to be manipulated by commands to theprocessor.

1. A method for forming a common ground for an microelectromechanicaldevice comprising acts of: patterning a common ground plane layer on asubstrate; forming a dielectric layer on the common ground plane layer;depositing a DC electrode region through the dielectric layer to contactthe common ground plane layer; and depositing a conducting layer on theDC electrode region so that regions of the conducting layer contact theDC electrode region, so that the common ground plane layer provides acommon ground for the regions of the conducting layer.
 2. A method forforming a common ground for an microelectromechanical device as setforth in claim 1, wherein the act of patterning a common ground planelayer on a substrate further comprises acts of: depositing a groundplane photoresist pattern to form a common ground plane layer on atleast a portion of a substrate having a substrate area; depositing thecommon ground plane. layer into the ground plane photoresist pattern;and removing the ground plane photoresist pattern.
 3. A method forforming a common ground for an microelectromechanical device as setforth in claim 2, wherein the act of forming a dielectric layer on thecommon ground plane layer further comprises acts of: depositing adielectric layer having a thickness and an area on the common groundplane layer; depositing a DC via photoresist pattern on the dielectriclayer, patterned to leave a DC electrode via exposed; etching throughthe thickness of a portion of the area of the dielectric layer at the DCelectrode via to form a DC via in the dielectric layer, where the DC viaconnects with the common ground plane layer; and removing the DC viaphotoresist pattern.
 4. A method for forming a common ground for anmicroelectromechanical device as set forth in claim 3, wherein the actof depositing a conducting layer on the DC electrode region so thatregions of the conducting layer contact the DC electrode region, so thatthe common ground plane layer provides a common ground for the regionsof the conducting layer further comprises acts of: depositing a DCelectrode region photoresist pattern; depositing a conducting layer onthe DC electrode region photoresist pattern and dielectric layer to forma set of DC electrodes in the set of DC electrode regions, where a DCelectrode is in contact with the common ground plane layer through theDC via; and removing the DC electrode region photoresist pattern.
 5. Amethod for forming a common ground for an microelectromechanical deviceas set forth in claim 4, further comprising acts of: depositing asacrificial layer over the conducting layer; depositing an anchor sitephotoresist pattern to provide for an anchor site; etching through thesacrificial layer to expose a portion of the conducting layer at a DCelectrode region to form an anchor site; removing the anchor sitephotoresist pattern; depositing an insulating first structure layer onthe sacrificial layer and the anchor site, the insulating firststructure layer having an area; depositing a top electrode photoresistpattern for etching through the anchor site for providing contact to theconducting layer and for forming a top electrode; etching through theinsulating first structure layer across at least a portion of the anchorsite so that a portion of the conducting layer is exposed, and etchingthrough the insulating first structure layer and through a portion ofthe thickness of the sacrificial layer at a top electrode site so that atop electrode space is defined through the insulating first structurelayer, and into the sacrificial layer, proximate an electrode region;removing the top electrode photoresist pattern; depositing a deviceseparation photoresist pattern on the insulating first structure layer,the device separation photoresist pattern forming separation regions forelectrically separating desired areas of the microelectromechanicaldevice and for separating desired devices; depositing a conductingsecond structure layer on the insulating first structure layer, theexposed portion of the conducting layer, and in the top electrode space,the conducting second structure layer having an area; removing thedevice separation photoresist pattern to eliminate unwanted portions ofthe conducting second structure layer in order to electrically separatedesired areas of the microelectromechanical device and for separatingdesired devices; depositing an insulating third structure layer on themicroelectromechanical device, across the substrate area, the insulatingthird structure layer having an area; depositing a device shapephotoresist pattern on the microelectromechanical device, across thesubstrate area, with the device shape photoresist pattern definingdesired device shapes by selective exposure; selectively etching throughexposed portions of the insulating first structure layer and theinsulating third structure layer to isolate an microelectromechanicaldevice having a desired shape; and removing the device shape photoresistpattern.
 6. A method for forming a common ground for anmicroelectromechanical device as set forth in claim 4, furthercomprising acts of: depositing a sacrificial layer on the dielectriclayer and the conducting layer, the sacrificial layer having athickness; and etching a plurality of tooth regions into the sacrificiallayer proximate a portion of the conducting layer, such that the toothregions, in a final device, provide a reduced adhesion area when thedevice closes.
 7. A method for forming a common ground for anmicroelectromechanical device as set forth in claim 6, furthercomprising acts of: depositing an anchor site photoresist pattern toprovide for an anchor site; etching through the sacrificial layer to anelectrode region in order to expose a portion of the conducting layer ata DC electrode region to form an anchor site; removing the anchor sitephotoresist pattern; depositing an insulating first structure layer onthe sacrificial layer and the anchor site, the insulating firststructure layer having an area; depositing a top electrode photoresistpattern for etching through the anchor site for providing contact to theconducting layer and for forming a top electrode space; etching throughthe insulating first structure layer across at least a portion of theanchor site so that a portion of the conducting layer is exposed, andetching through the insulating first structure layer and through aportion of the thickness of the sacrificial layer at a top electrodesite so that a top electrode space is defined through the insulatingfirst structure layer, and into the sacrificial layer, proximate anelectrode region; removing the top electrode photoresist pattern;depositing a device separation photoresist pattern on the insulatingfirst structure layer, the device separation photoresist pattern formingseparation regions for electrically separating desired areas of themicroelectromechanical device and for separating desired devices;depositing a conducting second structure layer on the insulating firststructure layer, the exposed portion of the conducting layer, and in thetop electrode space, the conducting second structure layer having anarea; removing the device separation photoresist pattern to eliminateunwanted portions of the conducting second structure layer in order toelectrically separate desired areas of the microelectromechanical deviceand for separating desired devices; depositing an insulating thirdstructure layer on the microelectromechanical device, across thesubstrate area, the insulating third structure layer having an area; anddepositing a device shape photoresist pattern on themicroelectromechanical device, across the substrate area, with thedevice shape photoresist pattern defining desired device shapes byselective exposure; and selectively etching through exposed portions ofthe insulating first structure layer and the insulating third structurelayer to isolate an microelectromechanical device having a desiredshape; and removing the device shape photoresist pattern.
 8. A methodfor forming a common ground for an microelectromechanical device as setforth in claim 1, wherein the act of forming a dielectric layer on thecommon ground plane layer further comprises acts of: depositing adielectric layer having a thickness and an area on the common groundplane layer; depositing a DC via photoresist pattern on the dielectriclayer, patterned to leave a DC electrode via exposed; etching throughthe thickness of a portion of the area of the dielectric layer at the DCelectrode via to form a DC via in the dielectric layer, where the DC viaconnects with the common ground plane layer; and removing the DC viaphotoresist pattern.
 9. A method for forming a common ground for anmicroelectromechanical device as set forth in claim 1, wherein the actof depositing a conducting layer on the DC electrode region so thatregions of the conducting layer contact the DC electrode region, so thatthe common ground plane layer provides a common ground for the regionsof the conducting layer further comprises acts of: forming a DCelectrode in set of DC electrode regions, where a DC electrode is incontact with the common ground plane layer through the DC via.
 10. Amethod for forming a common ground for an microelectromechanical deviceas set forth in claim 1, further comprising acts of: depositing asacrificial layer, the sacrificial layer having a thickness; and etchinga plurality of tooth regions into the sacrificial layer proximate aportion of the conducting layer, such that the tooth regions, in a finaldevice, provide a reduced adhesion area when the device closes.
 11. Amethod for forming a common ground for an microelectromechanical deviceas set forth in claim 1, further comprising acts of: depositing ananchor site photoresist pattern to provide for an anchor site; etchingthrough the sacrificial layer to an electrode region in order to exposea portion of the conducting layer at a DC electrode region to form ananchor site; removing the anchor site photoresist pattern; depositing aninsulating first structure layer on the sacrificial layer and the anchorsite, the insulating first structure layer having an area; depositing atop electrode photoresist pattern for etching through the anchor sitefor providing contact to the conducting layer and for forming a topelectrode space; etching through the insulating first structure layeracross at least a portion of the anchor site so that a portion of theconducting layer is exposed, and etching through the insulating firststructure layer and through a portion of the thickness of thesacrificial layer at a top electrode site so that a top electrode spaceis defined through the insulating first structure layer, and into thesacrificial layer, proximate an electrode region; removing the topelectrode photoresist pattern; depositing a device separationphotoresist pattern on the insulating first structure layer, the deviceseparation photoresist pattern forming separation regions forelectrically separating desired areas of the microelectromechanicaldevice and for separating desired devices; depositing a conductingsecond structure layer on the insulating first structure layer, theexposed portion of the conducting layer, and in the top electrode space,the conducting second structure layer having an area; removing thedevice separation photoresist pattern to eliminate unwanted portions ofthe conducting second structure layer in order to electrically separatedesired areas of the microelectromechanical device and for separatingdesired devices; depositing an insulating third structure layer on themicroelectromechanical device, across the substrate area, the insulatingthird structure layer having an area; depositing a device shapephotoresist pattern on the microelectromechanical device, across thesubstrate area, with the device shape photoresist pattern definingdesired device shapes by selective exposure; selectively etching throughexposed portions of the insulating first structure layer and theinsulating third structure layer to isolate an microelectromechanicaldevice having a desired shape; and removing the device shape photoresistpattern.
 12. A method of forming tooth regions on a metal portion of anmicroelectromechanical device comprising acts of: etching a plurality oftooth regions in to a sacrificial layer proximate a portion of aconducting layer; and depositing a metal layer over the sacrificiallayer such that portions of the metal layer conform with the toothregions to form teeth; whereby the conducting layer may be urged intocontact with another portion of the microelectromechanical device withthe teeth providing a reduced adhesion area.
 13. A method of formingtooth regions on a metal portion of an microelectromechanical device asset forth in claim 12, further comprising acts of: patterning aconducting layer on a substrate such that portions of the conductinglayer form electrodes; and depositing a sacrificial layer on portions ofthe substrate and the conducting layer, where the sacrificial layerdeposited is the sacrificial layer into which tooth regions are etched.14. A method of forming tooth regions on a metal portion of anmicroelectromechanical device as set forth in claim 13, furthercomprising acts of: depositing an anchor site photoresist pattern toprovide for an anchor site; etching through the sacrificial layer to anelectrode region in order to expose a portion of the conducting layer ata DC electrode region to form an anchor site; removing the anchor sitephotoresist pattern; depositing an insulating first structure layer onthe sacrificial layer and the anchor site, the insulating firststructure layer having an area; depositing a top electrode photoresistpattern for etching through the anchor site for providing contact to theconducting layer and for forming a top electrode space; etching throughthe insulating first structure layer across at least a portion of theanchor site so that a portion of the conducting layer is exposed, andetching through the insulating first structure layer and through aportion of the thickness of the sacrificial layer at a top electrodesite so that a top electrode space is defined through the insulatingfirst structure layer, and into the sacrificial layer, proximate anelectrode region; removing the top electrode photoresist pattern;depositing a device separation photoresist pattern on the insulatingfirst structure layer, the device separation photoresist pattern formingseparation regions for electrically separating desired areas of themicroelectromechanical device and for separating desired devices;depositing a conducting second structure layer on the insulating firststructure layer, the exposed portion of the conducting layer, and in thetop electrode space, the conducting second structure layer having anarea; removing the device separation photoresist pattern to eliminateunwanted portions of the conducting second structure layer in order toelectrically separate desired areas of the microelectromechanical deviceand for separating desired devices; depositing an insulating thirdstructure layer on the microelectromechanical device, across thesubstrate area, the insulating third structure layer having an area; anddepositing a device shape photoresist pattern on themicroelectromechanical device, across the substrate area, with thedevice shape photoresist pattern defining desired device shapes byselective exposure; and selectively etching through exposed portions ofthe insulating first structure layer and the insulating third structurelayer to isolate an microelectromechanical device having a desiredshape; and removing the device shape photoresist pattern.
 15. A commonground for an microelectromechanical device comprising: a substratelayer; a common ground plane layer formed on a portion of the substratelayer; a dielectric layer formed on the common ground plane layer andthe substrate layer, the dielectric layer formed with conductor spacestherein, where at least one of the conductor spaces is in contact withthe ground metal layer, the dielectric layer further including adielectric top surface; and a conducting layer formed as a set ofconductors in the conductor spaces of the dielectric layer, with atleast one of the conductors in contact with the common ground planelayer, the conducting layer having a conducting layer top surface, andwhere the dielectric top surface and the conducting layer top surfaceare formed in a substantially co-planar fashion to provide a planarizedsubstrate structure.
 16. A set of anti-adhesion tooth regions formed asa portion of an microelectromechanical device, with the set ofanti-adhesion comprising a plurality of tooth regions formed andextending from first portion of a microelectromechanical device, withthe tooth regions shaped such that when the first portion of themicroelectromechanical device is urged into contact with another portionof a microelectromechanical device, the tooth regions provide forreduced adhesion, thereby preventing adhesion of the first portion ofthe microelectromechanical device with the other portion of amicroelectromechanical device.